light-colored object records as a heavy-density (dark) area,  and  a  dark-colored  object  records  as  a  low-density (thin) area; therefore, a negative image is reversed compared  to  the  original  scene.  This  reversal  is produced by a bright object in the scene reflecting more light  than  a  darker  object.  The  greater  amount  of reflected light from the brighter object affects more silver  halides  in  the  emulsion. The portions of the negative where the most silver halides  have  been  affected  are  referred  to  as HIGHLIGHTS. The portions that are least affected are referred to as SHADOW AREAS. The light reflections from objects other than the brightest and darkest are referred to as MIDTONES. The amount of metallic silver deposit in any portion of a negative is referred to as density. The amount of light that a negative transmits in a given period of time is  controlled  by  the  density  of  the  metallic  silver deposits. Therefore, density is used to describe the light-stopping  ability  of  a  negative. The difference in densities between areas in a negative is known as contrast. The total contrast (density range) of a negative is defined as the difference in density between the least-dense shadow area and the most-dense  highlight  area  in  a  negative. Emulsion Latitude The inherent ability of a black-and-white film to record  a  range  of  scene  brightness  differences  as differences in density is termed emulsion latitude Normal- and low-contrast emulsions can record a wide range of scene brightness values and are considered to have  a  wide  emulsion  latitude  or  long  scale. High-contrast emulsions record a short range of scene brightness values and are considered to have a narrow emulsion  latitude  or  short  scale. Exposure   Latitude The amount the exposure can be varied (increased or decreased) from the ideal exposure and still provide an  acceptable  negative  is  termed  exposure  latitude. The least amount of exposure that records sufficient shadow detail generally provides the best quality negative and is considered the ideal exposure. The use of a determined exposure index leads to the ideal exposure  for  a  particular  film  and  process  combination. Generally, the use of the assigned ISO speed provides acceptable  results. Emulsion   Definition Several  factors,  including  graininess,  resolving power (resolution), and acutance, affect the definition or capability of an emulsion to produce a clear, sharp image. GRAININESS. –The negative image consists of nearly an infinite number of density deposits of metallic silver. To the naked eye, these grains of silver appear as a smooth, continuous deposit; however, when the image is magnified significantly, a speckled, granular, or mottledeffect  becomes  apparent.  This  appearance  of  the enlarged  image  is  called  graininess. The  graininess  of  a  negative  depends  upon  the  size of the silver halides in the emulsion, the exposure the emulsion received, and the clumping action of the metallic silver grains during development. Although each emulsion has an inherent grain size, the graininess effect in a negative can be minimized by giving the film correct  exposure  and  proper  development.  As  a  general rule,  slower  speed  emulsions  have  a  finer  grain (a smaller grain size) than faster speed emulsions. The Eastman Kodak Company uses modem tabular, or T-grain, technology in some of their emulsions. In doing so, flat, tabular crystals are used which are very efficient  in  absorbing  light.  In  T-grain  emulsions,  fewer silver halide crystals are needed, because the crystals have a relatively large surface area for light to strike, but are thin and contain a small amount of silver halides. These properties provide higher resolution and lower graininess compared to other films with the same relative  film  speed. Not all black-and-white films form the final image in black metallic silver; for example, Ilford’s XP-1 black-and-white  film  produces  a  dye  image.  The advantage of this technology is the film can be processed in color-processing chemicals along with color film and then  printed  on  black-and-white  paper. RESOLVING  POWER.–This is a term used to define the ability of an emulsion to record fine detail. The resolving power, or resolution, of an emulsion is expressed  as  line  pairs  per  millimeter.  Resolving  power is determined by photographing a lined test chart at a greatly reduced size then counting the lines present in one  millimeter  of  film. ACUTANCE.–This is the ability of an emulsion to produce sharp edges between image density differences. Do not confuse this with the ability of an emulsion to produce  sharp  images  controlled  by  lens  focus. Although an image is in focus, the line between a 2-4